Conversion of hydrocarbon oils



Patented Jan. 27, 1942 umrao STATE I 2,271,318 CONVERSION or HYDROCARBON OILS Charles L. Thomas and Jacob Elston Ah lberg, Chicago, 111., assignors to Universal Oil Prodnets Company, Chicago, 111., a corporation of Delaware No Drawing. Application January 6, 1941,

Serial No. 373,310

16 Claims.

This is a continuation-in-part of our co-pending application, Serial No. 176,648, filed November 26, 1937; which has matured into Patent No.

This invention relates to the conversion of hydrocarbon fractions produced. in distilling petrol'eum oils and especially those of a distillate character which are vaporizable without substantial decomposition. Q

In a more specific sense the invention'is concerned with a modification of hydrocarbon oil conversion processes involving .the use of particular and'specific' types of catalysts which tune tion to selectively promote the formation of low boiling gasoline fractions.

The art of cracking relatively heavy hydrocarbons to produce primarily gasoline or gas is very -extensive and it is recognized that most of the basic principles of hydrocarbon decomposition are known and that particular commercial processes have been developed which embody these principles. The application of catalysts, however, in cracking reactions is practically upon the same basis as it is in other fields, that is, there is much more to be learned about them. A considerable number of the catalysts developed for cracking have a tendency to accelerate reactions leading to the formation of gas rather than of gasoline, this being particularly evidenced by reduced metal catalyst such as nickel or iron and many of such catalysts are sensitive to sulfur poisoning and are quickly coated with carbonaceous materials which render them practically inert. This deposition of carbonaceous materialsis many times related to the type of decomposition reactions selectively fostered by the catalyst.

The present invention is concerned with the use of catalytic materials which are specially adapted to accelerate the cracking of heavy distillate fractions of petroleum and other hydrocarbonaceous materials to increase the rate of production of high antiknock gasoline-boiling range fractions and gaseous lay-products which contain unusually high percentages of readily polymerizable olefins which are a potential source of further gasoline yields. The preferred catalysts for the process are characterized by selectivity in accelerating gasoline-forming reactions rather than light gas-forming reactions, by their selectivity in producing high antiknock gasoline, by their refractory character which enables them to retain their catalytic properties under severe conditions of temperature and pressure, by their case and simplicity of manufacture and their exact reproducibility.

n In one specific embodiment the present tion comprises a method forconverting hydrocarbon distillate fractions containing substantial- '15! no gasoline into material yields of gasoline and gases containing relatively high percentages .inven- In the case of alumina of polymerizable olefins by subjecting the vapors of such distillates at elevated temperatures and substantially atmospheric pressure to contact move substantially all alkali metal ions and calcined at elevated temperatures to produce highly refractory alumina-silica particles which are able to withstand for long periods of time the alternate service and reactivation periods.

We have found that the alumina-silica catalysts whose use characterizes the present cracking process and which may be prepared by several alternate methods described in more detail in succeeding paragraphs are rendered much more active and selective in accelerating gasolineforming reactions in cracking when the originally precipitated hydrated alumina and hydrated silica which go to form the primary composites in various proportions are completely freed from alkali metal ions which in most instances will be sodium ions because the sodium salts of silicic acids are cheapest and most readily available for the manufacture of this type of catalyst. The primary step in the method of preparing the catalyst whose use in cracking-characterizes the present invention may be varied somewhat and the following is a general summary of the alter-' native modes of operation which may be emv ployed: k

'1. Solutions of soluble alkali metal silicates and soluble aluminum salts, the latter including soluble aluminates, may be mixed in varying proportions to jointly precipitate hydrated alumina and hydrated silica.

2. Hydrated silica be separately precipitated and the precipitates mixed in the wet condition. In the case of silica a convenient method is to acidify a solution of an alkali metal silicate to precipitate a silica gel. the desired hydroxide may be precipitated by the addition of alkalis. particularly ammonium hydroxide although other precipitants such as ammonium carbonate, ammonium hydrosulfide or ammonium sulfide may be employed.

3. A separately precipitated hydrated silica may be added to an aqueous solution of an aluminum salt and the hydrated alumina precipitated in the presence of the suspended silica by the addition of alkaline precipitants.

4. A separately precipitated hydrated alumina may be added to an alkali metal silicate and the silica precipitated in the presence of the alumina and hydrated alumina may hydrated alumina may be employed within the scope of the invention although obviously the character and 'eificiency of the ultimately prepared alumina-silica masses will vary somewhat with the exact conditions of precipitation and the ratio of alumina to silica. For example, one proportion may 'furnish catalysts better for use in reforming a certain gasoline boiling range material, another may be better for use in the cracking of a gas-oil distillate and still another may be better adapted to cracking still heavier fractions.

An important feature of the present invention resides in the fact that cracking operations, particularly in petroleum distillates, may be conducted with greatly increased efllciency .when silica-alumina catalysts are employed which have been subjected to treatment to efl'ect substantially complete removal of alkali metal ions from the primary hydrated alumina-silica masses prior to their calcining to prepare them for service. It is not known whether the alkali metal salts such as sodium are present in the primary hydrated composites in chemical combination or in an adsorbed state but it has been definitely determined that their removal is necessary if catalysts of superior value in accelerating cracking reactions are to be obtained. It is probable that the presence of these alkali metal ions causes a sintering or fusion of the surfaces of ,the primary composites during the heating period so that the porosity of the catalyst particles is much reduced with a, corresponding reduction in efiective surface, considering the catalytic effects to be due at least in part to surface action. However, such concepts are principally speculations in view of the difliculty of obtaining direct v confirmatory evidence.

In preparing catalyst for the process several alternative methods are available applicable to difierent primary hydrated silica-hydrated alumina composites to insure the substantially complete absence of sodium or other alkali metal ions. One method consists in washing the primary hydrated silica with suflicient quantities of hydrochloric acid to extract alkali metal by the formation of chlorides and possibly introduce hydrogen into the catalyst composites. Thus a precipitated hydrated s lica mass may be first washed by decantation with waterand flltered by pressure or suction to remove the major portion' of the soluble impurities. -The precipitate is then removed from the filter and treated with relatively dilute hydrochloric acid, washed 'anynecessary number of times and again tr'ans-' ierred to'a pressure or suction filterand freed from the major portion of the-adhering water. As an alternative method for removal 01' alkali metals which maybe present in the chemically combined or adsorbed condition, the'precipitated silica may be washed with solutions or ammonium chloride which apparently serves to replace sodium with ammonium, which is later volatilized in the drying and calcining ofthe silica either before or after admixture with the alumina; The desired amount of hydrated alumina may be precipitated on the siliceous mate-1 rial or freshly precipitated hydrated alumina may be addedand mechanically mixed therewith.

Another method which has been found to be cincacious in the preparation of cracking catalysts consists in washing theprimary hydrated silica-hyd ated alumina precipitates or composites with solutions 01' ammonium compounds such as, for example, the chloride or other haiides, the sulfate, the nitrate, or the acetate, so that the ammonium ion appears as a constituent of the catalyst composite and is later expelled from combination or adsorption in the calcining steps, leaving a structure of relatively high porosity in so doing. As a variation of this method the co-precipitation or mixing of the primary hydrated silica and alumina may be brought about in the presence of ammonium hydroxide or any of the other salts of ammonium already mentionedin suflicient excess to insure an adequate removal of the alkali metal ion. In the case of co-precipitation it has been found that the necessary excess 01 ammonia is present at the point corresponding to a suflicient coagulation of the gel structure of the primary precipitates to permit ready filtering and washing. In other word it sumcient ammonia has been used to insure easy washing and filtering the alkali metal salts have been-generally reduced to a point at which they no longer have any appreciable adverse influence on the catalyst properties.

The weight of evidence at hand on the mechanism leading to the replacement of alkali metals in the primary hydrated silica precipitates or the silica-alumina masses indicate that the alkali metals are held by adsorption rather than by chemical bonds. This is indicated by the iact lar manner to that described in the case or ammonium chloride. For example, a primary comv posite containing undesirably large amounts of alkali metal even after repeated water washing may be again suspended in water and treated with a solution of salts of such metals as alus minum, magnesium, calcium, manganese, cerium, or other multivalent metals in which the metal forms the positive ion of the salt being used.

As a further example, the washing may first be with an acid solution or an ammonium salt solution as above described preliminary .to treating with solutions of the multivalent salt solutions.- Obviously such replacements may be allowed to proceed with consequent variation in the properties of the final catalyst. This method of operation permits the production of catalysts of a high degree of variability which are obviously nonequivalent in regard to their effect upon a given cracking reaction;

After a ilnal washing of the hydrated aluminasilica mix, it'is recoveredas a filter cake by using any known type of suction or pressure filter and is then heated to a temperature of the order of 300 F. for a period or 36 to 48 hours after which it may be ground and sized to recover particles or a convenient average diameter or formed into any desired by compression methods. It has been found that the drying at 300 F. produces material having a total watercontent of about 15% by weight which asalready stated apparently corresponds to the best workability oi the material. By calcining at cracking temperaturesof the order or approximately 850-1000 FL,

a further dehydration occurs so that for example after a considerable period of heating at 900 F., thewater content as-determined by analysis is of the order of 2-3% which is firmly fixed and does not appreciably vary either as the result of long service or a large number of reactivations at conly higher temperatures. I

the spent particles to burn off deposits of carbonaceous material at temperatures as high as, 1400-1600 F. without material loss of catalytic activity.

According to the present process catalysts prepared by the general procedure'described in the preceding paragraphs are utilized to the best advantage in cracking reactions when employed as filling material in tubes or chambers in the form of small pellets or granules. In the majority of cases wherein hydrocarbon fractions readily vaporizable at moderate temperatures without extensive decomposition are employed, the average particle size is within the range of 6-10 mesh, which may apply either to small pellets of uniform size and short cylindrical shape or to particles of irregular size and shape produced by the grinding and sizing of the partially dehydrated materials. While the simple method of preheating a given fraction of hydrocarbon oil vapors to a temperature suitable for their cracking in contact with the catalysts'and then passing the vapors over a stationary mass of catalyst particles may be employed in some cases, it is usually preferable to pass the preheated vapors through banks of relatively small diameter catalyst-containing tubes in multiple connection between headers, since this arrangement of apparatus is better adapted to permit .exterior heating of the catalyst tubes to compensate for the heat loss in the endothermic cracking reactions.

After the passage of the oil vapors over the catalyst, the products may be separated into material unsuitable for further cracking, intermediate insufficiently converted fractions amenable to further catalytic cracking, gasoline boiling range materials and gases, the intermediate fractions being returned directly to admixture with the charging stock 'so that ultimately there is complete recycling of all fractions and maximum utilization of the charging stock-for gasoline production. v

The present process besides being characterized penetrate to a considerable distance by the use of novel catalysts is further character- I ized by the use of moderate temperatures, relatively; low pressures and high throughputs in comparison with strictly thermal cracking processes in use at the present time. When dealing with intermediate distillate fractions of the character of gas oil, it is seldom necessary to employ temperatures greatly in excess of 950 F. in the catalytic conversion zone. In the matter of pressure, it is seldom desirable to employ those materially above atmospheric except in so far as this is necessary 'tojinsure a proper flow through the vaporizing and cracking zonesand the sucwashingsare free ceeding fractionating equipment. However, since pressure increases the capacity of both cracking and fractionating units, moderately superatmospheric pressures may be employed when their use is dictated by the overall economy of the process. The times of catalytic contact are. relatively short and of the order of 1-10 seconds.

The following examples of preparation and use of the types of catalysts peculiar to the present invention are given to indicate their novelty and utility in practical cracking processes although not for the purpose of limiting the invention in exact agreement'with the data introduced.

Example I v The method of catalyst preparation in this case is to mix an alkali metal silicate and an acid to form a hydrated silica, mixing thehydrated silica with a solution of an aluminum salt and precipitating hydratedalumina and purifying the composite.

A solution is prepared containing 415 grams of water glass of approximately 40 Baum in 5 liters of water. Approximately 500 cc. of 2.5 molar hydrochloric acid is slowly added to the diluted water glass solution while stirring. The silica hydrogel is filtered and washed with water and then suspended in approximately 500 cc. of

water containing approximately 40 grams of aluminum chloride hexahydrate in solution. Ammonium hydroxide is then added to precipi tate the alumina hydrogel in the presence of the hydrated silica and the composite of hydrated alumina and hydrated silica is then washed with a solution containing approximately 20 grams per liter of manganese chloride until the final from sodium when tested with a uranyl acetate reagent. The purified catalyst preparation is then recovered as a filtercake which is dried at approximately 932 F. when granules of the above prepared catalyst are disposed in a catalyst chamber and contacted with a Pennsylvania gas oil which has been vaporized and preheated to a temperature of 932 F. and passed through the catalyst at an hourly liquid space velocity of approximately 4, the following results are obtained: a

\ Data' on cracking experiments Run #1 Run *2 Temperature average at center of catalyst 892 898 Gasoline 400 F. E. P.:

Volume, er cent.. 29. 2 28. 8 A.P.I., F 10.1 60.3 Octane number, motor method 77. 2 77. 0 Engler distillation:

I. B. P., "F 89 10%, F 117 120 m, 137 147 30%, 174 507 F 225 230 7 296 301 90%, 345 302 E. P., "F 401 399 Gases (boiling range below +l0 F.

. Weight, percent (total) 6. 8 5. 9 Molecular we1%ht 35. l 31. 2 Propane and utenes, weight percent oi charge 4. 7 4. 1

Gas oil recovered (recycle stock): 1

Volume, percent 62. 9 62. 8 A I.,60F 39.2 39.1

Example II I alumina in the presence of the suspended purified -hydrated silica by the addition of an alkaline precipitant free from alkali metal impurities.

About 415 grams of approximately 40 Baum water glass is diluted with liters of water and approximately 500 cc. of 2.5 molar hydrochloric acid is added thereto gradually while stirring to precipitate a hydrated silica. The hydrated silica is Washed several times with water and then with a solution containing approximately 25 gramsof manganese chloride per liter until the washings are free from sodium when testing with a. uranyl acetate reagent. The purified silica hydrogel is then suspended in approximately 500 cc. of water containing 40 grams of aluminum chloride hexahydrate and hydrated alumina precipitated in the presence of the silica hydrogel by the addition of ammonium hydroxide. hydrated alumina is then recovered as a filter cake and dried at a temperature of approximately 275 F. The dried material is crushed to pass a 40 mesh screen, mixed with a lubricant and pilled to form A -inch pellets. The pilled catalyst is calcined at a temperature of approximately 1500 F.

A Mid-Continent gas oil is vaporized and preheated to a temperature of approximately 932 F. andis contacted with the pelleted catalyst above described at substantially atmospheric pressure in a once-through operation. Approximately 24.2% by volume of the charge of 400 F. endpoint gasoline is produced having octane number of '78 by the motor method.

We claim as our invention:

1. A process for converting hydrocarbon distillates heavier than gasoline into substantial yields of gasoline which comprises subjectin said distillate under cracking conditions to contact with a catalyst produced by separately precipitating hydrated aluminum oxide and bydrated silicon dioxide containing ,alkali metal ions, freeing the precipitated materials of alkali metal ions, by treating with a solution of a salt of manganese, mixing the purified materials in the wet condition, and drying to remove a major portion of the total water content.

2. A process for converting-hydrocarbon dis-' tillates heavier than gasoline into substantial yields of gasoline which comprises subjecting said distillates under cracking conditions to contact with a catalyst free of alkali metal compounds and produced 1., separately precipitating hydrated aluminum oxide and hydrated silicon dioxide containing alkali metal ions, mixing said separatelyproduced precipitates in a wet condition, adding a sumcient quantity of a manganese compound to replace combined or adsorbed alkali metal ions present in the precipitate with manganese, filtering and washing the precipitated material to substantially complete removal of'soluble substances and heating the washed precipitateto remove the major portion of its total water content.

3. A process for converting a hydrocarbon distillate heavier than gasoline into substantial yields of gasoline which comprises subjecting said distillate under cracking conditions to con- Thecomposite of hydrated silica and mixing said-separately produced precipitates in a wet condition, filtering and washing the precipitated material to substantially complete removal of soluble substances. and heating the washed precipitate to remove the major portion of its total water content.

4. A process for converting hydrocarbon dis tillates heavier than gasoline into substantial yields of gasoline which comprises subjecting said distillates under cracking conditions to con-= tact with a catalyst free of alkali metal com" pounds and produced by separately precipitating hydrated aluminum oxide and hydrated silicon dioxide, treating said hydrated silicon dioxide with a solution of a manganese salt to remove combined or adsorbed alkali metals ions, mixing said separately produced precipitates in a wet condition, filtering and washing the precipitated material to substantially complete removal of soluble substances and heating the washed precipitate to remove the major portion of its total water content.

5. A process for converting hydrocarbon dis,- tillates heavier than gasoline into substantial yields of gasoline which comprises subjecting said distillates under cracking conditions to con:- tact with a catalyst free of alkali metal compounds and produced by separately precipitating hydrated aluminum oxide from a solution of a soluble aluminate and hydrated silicon dioxide by the acidification of an alkali metal silicate solution, mixing said separately produced precipitates in a wet condition, adding a suflicient quantity of a manganese salt to replace combined or adsorbed alkali metal ions present in the precipitate with manganese, filtering and washing the precipitated material to substantially. complete removal of soluble substances and heating the washed precipitate to remove the major portion of the total water content.

6. A process for converting a hydrocarbon distillate heavier than gasoline into substantial yields of gasoline which comprises subjecting said distillate under cracking conditions to contact with a catalyst produced by precipitating hydrated aluminum oxide from an aqueous solution of a soluble aluminum compound, separately precipitating hydrated silicon dioxide from an aqueous solution of an alkali metal silicate, combining the precipitates in undried condition and-removing from the hydrated silicon dioxide alkali metal ions present therein as-a result of its precipitation from the alkali nietal silicate solution by washing with a solution of a manganese salt,- and calcining the commingled precipitates.

7. A conversion process which comprises contacting normally liquid hydrocarbon oil under cracking conditions with-acatalyst produced by precipitating hydrated silicon dioxide containing alkali metal ions, precipitating hydrated aluminum oxide, treating resultant precipitated material, containing said alkali metal ions, with I drying the mixture to remove the major portion tact with a catalyst free of alkali metal compounds and produced .by separately precipitat .ing hydrated aluminum oxide and hydrated silicon dioxide, adding a suflicient quantity of a soor adsorbed alkali metal ions with manganese,

of its water content.

8. The process as defined in claim 7 further characterized in that the hydrated aluminum oxide is substantially free of alkali metal'ions and the hydrated silicon-dioxide is treated with saidsolution prior to combining it with the hydrated aluminum oxide, the latter being precipcipitated prior to the alumina hydrogel and susitated in the presence of the hydrated silicon dioxide. 1

9. The processes defined in claim 7 further characterized in that the aluminum oxide and silicon dioxide are co-precipitated and the admixed precipitates treated with said solution..

10. The process as defined in claim 7 further characterized in that the aluminumoxide and silicon dioxide are precipitated independently of each other.

11. The process as'defined in claim 7 further characterized in that said oil is a distillate heavier thangasoline. l 121. A conversion processwhich comprises subjecting the hydrocarbon oil to cracking conditions in the presence of acalcined mixture of separately precipitated alumina hydrogel and silica hydrogel, said hydrogels having been combined in undried condition prior to the calcination and said silica hydrogel having been sub stantially freed oi. alkali metal compounds by washing with a solution of a salt of manganese. 13. The process as defined in claim 12 further characterized in that the silica hydrogel is precipitated prior to the alumina hydrogel and the latter thereafter precipitated in the presence of the silica hydrogel.

14. The process as characterized in that the silica hydrogel is predefined in claim 12 further pended in an aqueous aluminum salt solution, the alumina hydrogel being combined with the silica hydrogel by precipitating the same from said solution in the presence of the silica hydrogel.

15. A conversion process which comprises con-- tacting normally liquid hydrocarbon oil under cracking conditions with a catalyst produced by precipitating hydrated silicon dioxide containing alkali metal ions, precipitating hydrated aluminum oxide, treating resultant precipitated material containing said alkali metal ions with an aqueous acid solution and with a solution or a manganese salt to remove alkali metal ionsand combining the precipitated aluminum oxide and silicon dioxide in undried condition. and drying the mixture to remove a major portion or its water content.

16. The process as defined in claim 15 further characterized in that the hydrated aluminum oxide is substantially free from alkali metal ions and the hydrated silicon dioxide is treated with said solutions prior to combining it with the hydrated aluminum oxide, the latter being precipitated in the presence of the hydrated silicon dioxide.

- CHARLES L. THOMAS.

JACOB ELSTON AHIBERG. 

